Ms Polk lacks basic knowledge of American History. A significant number of early NEGROES in Colonies were never slaves. they and their descendants were Free People of Color. Most were not black either. Some were slave Owners.
Africa is a continent (not a genetic pool) that includes Egypt, Algeria and Israel. Those folks are not Negroes, nor are the Bushmen, Boers etc. all are Africans.
The Melugeons very possibly are NOT descended from slaves, rather displaced FPC.